Signaling apparatus



Aug. 19, 1947. J. T. NElswlNTER SIGNALING APPARATUS Filed Dec. 12, 1942 ms@ SSRN T526 TEQW llllll. Nm. ..nNovo v INVENTQR l JZ/V/easwzmter BY g1 ig Y EZ' Z ATTORNEYA Patented Aug. 19, 1947 SIGNALING APPARATUS James T. Neiswinter, South Orange, N. J., assignorto American Telephone and Telegraph Company, a corporation of New York Application DecemberflZ, 1942, Serial No. 468,862

Claims.

This invention relates to signaling systems and more particularly to appaartus lor selectively transmitting signals to any oneoi a plurality of diiierent points.

One form of signaling or ringing system in use at present, for example, for signaling any one of a plurality of parties connected to a telephone or other line involves the simultaneous transmission of a predetermined number of dots and dashes to a plurality of parties. These dots and dashes produce currents which are rendered audible at each partys station. The dots and dashes assigned to a particular party forma distinctive code which is diierent from the code assigned to all other parties and, although all parties hear all of the codes, the only party who will answer the call will be the one whose ringing code has been received. This type of ringing system requires all of the parties to listen to all of the codes received so that each party may be ready to respond only to the code assigned to him. Y

In order to providea more selective and positive ringing system, a novel arrangement has been devised requiring, among other things, a standard dial at each subscribers oflice and apparatus at the central office to respond to the manipulations of the dial at any Subscribers ofce. In the proposed arrangement, a subscribers dial may be operated a predetermined number of times in accordance with a prearranged code, and the dial will produce a corresponding number of groups of clicks or surges. Each group of clicks or surges will be impressed upon a transformer or repeating coil which is connected tothe main line, whereupon a series of alternating current spurts will be transmitted over the line to the central office. At the central office the received currents will actuate apparatus including a rotary selector to select any one of a plurality of lines to the exclusion of all other lines. Only one of the parties will 'be signaled by the calling party.

To illustrate the invention it may be assumed that a calling party has dialed four digits such as 0505 in succession in accordance with one of the preassigned codes. The iirst digit-which is zero-will produce a long train of spurts which will` clear the apparatus at the central oce and prepare it to respond to the remaining three digits 505 which are employed to selectively Signal one of the various subscribers stations. The system is arranged to condition the central office apparatus for switching operations only when a digit such as No. Ogis the rstdigit, but the remaining digits determine the subscribers line which will be connected directly to the calling party through the central oice.

One of the objects of this invention is to selectively signal any one of a plurality of stations by spurts caused by operation of the dial and to prevent the signal from effecting the switching operation unless the first digit dialed is a predetermined digit. If the rst digit required is a Zerowhich produces a long series of spurts-the switching apparatus will then, and only then, be prepared by this digit while on the other hand the central oiice apparatus will be substantially nonresponsive to ordinary voicel currents.

The switching apparatus of this invention includes a rotary selector so connected to the system that the selector will be operated only when the first dialed digit is the predetermined digit. The rotary selector will then be stepped by each additional dialed digit to assist in signaling the desired station.

This invention Will be better understood from the more detailed description hereinafter following when read in connection with the accompanying drawing in Which Figure 1 represents one embodiment of the invention, and Fig. 2 illustrates one of the Various circuits controlled by the switching apparatus of Fig. 1.

The general operation oi the system will now be outlined. Assume that the subscriber operates dial D to dial No. 0. This will cause a long train of alternating current spurts to be transmitted over line E, as described in my Patent No. 2,367,-

042, issued January 9, 1945. Relay P will follow theY train of spurts to control the subsequent equipment.` Relay SM will be released with the first operation of relay P, and it will remain released during the receipt oi the spurts of the first digit. Relays F and Z, however, will be operated in that order in response to the spurts of the first digit. The rotor magnet Rn of selector SE will vbe operated to advancethe selector arm D1 to its first contact No. l and at the same time closeV the oli-normal contacts ON.

During the interval between the successive groups of spurts of the rst and second digits dialed by dial D, tube VS will become ionized, relay SM will become operated, and relays F and Z will release. Ii the second dialed digit is a No. --thereby producing a substantially shorter train of spurts-relay F will operate and in turn step the arm D1 of selector SE to its second contact No. 2. However, if the second digit Were a No. 0 instead of a No. 5, .both relays F and Z would beagain operated in that order, the selector SE would also step its arm D1 to its contact No. 2 and relay S2 would be operated and locked up. The third dialed digit, if a No. 5, will operate relay F and at the same time step the arm D1 of selector SE, but relay S3 will remain unoperated. However, if the third digit is a No. 0, both relays F and Z will be operated, arm D1 of the selector stepped to contact No. 3, and relay S3 operated, Similarly, the fourth digit will cause either relay F or relays F and Z to operate, depending upon whether the fourth digit is No. 5 or No. 0, and then step arm D1 to its contact No. 4, and then operate relay S4 only if the fourth digit is No. 0. The relays S2, S3 and Si will be arranged to apply voltage to one of eight terminals Ki-Ks to selectively ring the station connected to the particular terminal having the applied voltage. After the arm D1 of selector SE has reached its last terminal and a predetermined interval of time has elapsed, relay R will be operated, whereupon the release magnet RL of selector SE will be operated to restore all of the relays and the selector arm D1 to their initial condition. The system is so arranged that relay R will be operated also if there is a delay of a predetermined interval in dialing the four digits of the code, in which case all of the apparatus will also be restored to its initial condition.

The description of the operation of the system has thus far been general. More specifically the apparatus operates as follows:

When dialing No. 1, for example, the primary circuit of transformer A is opened once and closed OnCe by the contacts of dial D. With the opening of this primary circuit, a surge of current traverses the primary of transformer A, and a similar and second surge traverses the primary of transformer A with the closure o-f the primary circuit. Each of the two surges of current in the primary of transformer A, therefore, produces a complete and independent cycle of current in the secondary of transformer A- Thus b-y dialing No. 1, two complete waves or cycles are transmitted by transformer A to line E. Hence by dialing No. 5, ten complete cycles will be transmitted over line E. Furthermore, by dialing No. 0 (which is equivalent to dialing a No. twenty complete cycles are transmitted over line E. These cycles are, of course, not pure sine waves, but transients. As the dial D is of a type which is generally timed to produce these twenty cycles in about one second, the transients produced and transmited over line E will be at a twenty-cycle rate. Similar transients are produced upon dialing any other number. However, the number of transients produced and transmitted over line E will simply be twice the nurnber dialed by dial D. Hence when dialing No. 5, ten transients will be produced and transmitted over line E, and these ten transients will occur within about one-half of a second.

The filter F is intended to pass that portion of the frequency band of the transients which lies at approximately 1,000 cycles. That is, filter F may pass all currents between about 800 cycles and 1,200 cycles and substantially suppress currents of all other frequencies. In general, filter F transmits to tube VD current of about 1,000 cycles interrupted twenty times per second. In other words, filter F transmits separate and distinct spurts of 1,000 cycle current every twentieth of a second.

Each such spurt of 1,000 cycle current will render the grid of tube VD positive with respect to its cathode 1,000 times per second, but the relay Vo, being too sluggish to follow the 1,000 cycle pulses of rectified current, will operate and release twenty times per second. Each 1,000 cycle spurt will cause the armature of relay Vo to close its M contact. The armature of relay Vo will, of course, be released from its contact S between successive 1,000 cycle spurts. Hence relay V0 will follow the 1,000 cycle spurts, becoming operated upon receipt of each such spurt and released when no such spurt is present. The armature of relay Vo will, therefore, translate the successive spurts of 1,000 cycle current into mechanical vibrations occurring at a rate which is determined by the interruptions of the 1,000 cycle spurts received through filter F.

In the idle condition, relay Vo and P are released. Condenser CS is charged by battery B1 through a circuit which includes resistors l0 and i l. The voltage across condenser CS is sufficient to ionize the gas between the control electrodes of tube VS and hence relay SM is operated, the operating circuit including battery B2, resistor l2, the winding of relay SM, resistor i3, the lower armature and back contact of relay P, the anode and lower control electrode of tube VS and ground. Relay SM remain locked in its operated condition during the idle period, the locking circuit including battery Bz, resistor i2, the winding of relay SM, resistor i3, the inner upper armature and make contact of relay SM, the back contact and outer upper armature of relay P and ground. During the idle condition the other tubes will remain in deionized condition and all other apparatus will be unoperated.

Upon the receipt of the first transient transmitted over line E through filter F pursuant to the operation of dial D, relay Vo will become operated and in turn cause relay P to operate. The operation of relay P removes ground from the winding of relay SM previously provided by circuits including the lower and upper inner armatures of relay P. Relay SM, therefore, releases. The operation of relay P transfers the winding of relay SM from the anode circuit of tube VS to the anode circuit of tube VM, the new circuit for relay SM including battery B2 resistor i2, the winding of relay SM, resistor le, the lower armature and make contact of relay P, the anode and lower control electrode of tube VM and ground. Condenser CM, previously grounded through the upper inner armature and back contact of relay P, is now ungrounoled and charged by battery B1 over a circuit which includes battery B1, resistor il, resistor I4, condenser CM, resistor l and ground. The constants of resistor ifi and condenser CM are so chosen that the normal length of the spurt received by a dial operation will not be sufficient to allow the condenser voltage to reach the value required to ionize the gas within tube VM and hence relay SM will remain released. At the same time condenser CS will discharge to gro-und connected to the inner upper armature and make contact of relay P.

At the end of the pulse, relays Vn and P will release. Condenser CS will then begin to receive a charge from battery B1 over the previously described circuit of resistors I0 and l l. The constants of resistor I0 and condenser CS are so chosen that during the normal interval between two successive pulses or spurts the condenser voltage will not reach the Value required to ionize the gas within tube VS and, therefore, relay SM will remain released. At the saine time condenser CM will discharge to ground connected to the inner upper armature and back contact of relay P.

Relay Vo and P follow the successive spurts or pulses transmitted by the operation of dial D, these relays both operating with each spurtl received and releasing at the end of each spurt. Assuming that the spurts produced by dial D are those coming from a dial of normal speed, condensers CM and CS will be alternately charged and discharged, as already noted. However, the charging intervals of condensers CM and CS are insufficient to allow these condensers to reach the ionization voltages of tubes VM and VS, respectively, and, therefore, relay SM will remain released.

As long as relay SM remains released, condenser CF will be receiving a charge from battery B1 over a circuit which includes battery B1, resistors lI and I8, condenser CF, resistor I9 and ground. The constants of condenser CF and resistor I8 are so chosen that the voltage on condenser CF will not reach the value required to ionize the gas of tube VF unless condenser CF has been receiving a charge from battery B1 for at least a predetermined interval of time as, for eX- ample, three-tenths of a second. When condenser CF is charged for that length of time, tube VF will become ionized and cause relay F to operate. The operating circuit for relay F includes battery B2, resistor l2, the lower armature and back contact of relay SM, the winding of relay F, the anode circuit of tube VF and ground. By dialing the digit No. at dial D, there will be produced a train of spurts extending over about livetenths of a second in a normal speed dial. Such a series of pulses will cause relay F to operate and remain operated for about two-tenths of a second. This margin of two-tenths of a second is provided to allow relay F to operate even in response to proper dial of somewhat faster dials.

The operation of relay F removes ground from condenser CZ previously connected thereto by the inner upper armature and back Contact of relay F. Condenser CZ then begins to receive a charge from battery B1 over a circuit which includes battery B1, resistor I I, resistor 2i, condenser CZ, resistor 22 and ground. Resistor 2l and condenser CZ are so chosen that the voltage on condenser CZ will not reach the value required to ionize the gas within tube VZ unless the received train of dial pulses lasts for a predetermined interval of time such as seven-tenths oi a second. When a series of spurts of that duration is received, tube VZ will become ionized and relay Z will become operated. The operating circuit for relay Z includes battery Ba, resistor 24, the lower inner armature and make Contact of relay F, the winding of relay Z, the anode circuit of tube VZ and ground. In tube VZ, as in other tubes, the anode circuit includes the anode or plate electrode and the lower input electrode which in each case may be grounded as shown.

Tube VZ will become ionized and relay Z operated in response to the pulses produced when dialing a No. 0, but will not respond to the pulses corresponding to the dialing of a No. 5. Thus the apparatus at the central oiiice or switching point will distinguish between the two groups of spurts corresponding to Nos. 5 and G.

The apparatus at the central cnice is so set up that a number, such as No. 0, must be dialed initially to prepare the apparatus for subsequent switching operations and to prevent false operation of the apparatus in response to undesired signals or spurts. When a No, 0 is dialed, the rotor magnet Ro of selector SE will be operated, the operating circuit of the magnet including battery B4, the winding of the magnet Ro, the

6. lower armature and make contact of relay Z and ground, In response to the operation ofthe magnet, the arms D1 and D2, which are mounted 0n a common shaft, will be stepped to their contacts No. l and at the same time close the oil-normal contacts ON. li a No. 5 had been dialed instead of No. 0, the relay Z would not have been operated and magnet Ro would have remained unoperated.

At the end of the train of spurts corresponding to the first digit dialed, relays Vo and P release, as already explained. The release interval is sufncient to allow condenser CS to become charged by battery B1 to the voltage required to ionize tube VS. Relay SM then operates by the completion of its circuit through the anode pathof tube VS and relay SM then locks in its operated position. rihe locking circuit includes battery B2, resistor iii, the winding of relay SM, resistor I3, the upper inner armature and make contact of relay SM, the upper outer armature and back contact of relay P and ground. The operation of relay SM releases relay F by opening its circuit at the back contact of the lower armature of relay SM. Moreover, relay Z becomes released due to the opening of its circuit at the make contact of the lower inner armature of relay F. The central oi-hce equipment is now ready to receive the second series or spurts or pulses corresponding to the second digit dialed by dial D. f

if the second digit dialed is No. 0, both relays F and Z will be operated in the manner already outlined hereinabove. In response to the operation of relay Z, the rotor magnet R0 will again be energized over the circuit completed through the lou er armature and iront contact of relay Z. Consequently the arms Di and D2 of the selector SE will advance to their No. 2 contacts. As the arm D1 reaches its No. 2 contact, relay S2 will become operated over a circuit including battery B5, resistor 25, the winding of relay S2, contact No, Z and ann D1 of the selector, resistor 26, the upper armature and make contact of relay Z and ground, Relay S2 will also be locked in its operated position, the locking circuit comprising battery B5, resisto-r 25, the winding of relay Sz its uppermost armature and make contact, resistor 2l, the lower armature and back contact of relay R and ground,

.lf the second digit dialed is No. 5 (instead of No. u), relay F will be operated but relay Z will remain unoperated. The rotor magnet Ro will also be energized over a circuit which includes battery B4, the winding of magnet Ro, the upper swinger and make contact of the off-normal switch ON, the upper outer armature and make contact of relay F and ground. The opposite terminals ci the winding of relay S2 will be connec-'sed to batteries B5 and Bt over a circuit which includes battery B5, resistor 25, the winding of relay S2, the arm D1 and its contact No, 2, resistor 25, the upper armature and back contact of relay Z, resistor 29, battery Bs and ground. As these two batteries are of equal potentials, relays Sz will remain unoperated.

if the third digit dialed is No. O, relays F Z will be operated and the arms D1 and D2 will be stepped to their third contacts No. 3. The operation of relay Z will cause relay S3 to become operated over a circuit including battery B7, resistor 3l, the winding of relay S3, arm D1 and its contact No, 3, resistor 26, the upper armature and make contact of relay Z and ground. However, if the third digit is a No. 5, relay F will be operated and arms D1 and D2 stepped to contact No. 3l,

7. but relay Z will remain unoperated. Consequently relay S3 will remain unoperated.

If'the fourth digit dialed is No. 0, relays F and Z will be operated, the arms D1 and D2 stepped to their contacts No. 4, and relay S4 then operated. The operating circuit for relay S4 includes battery B8, resistor 32, the winding ofv relay S4, the lower armature and make contact of relay F, arm D1 and its contact No. 4, resistor 26, the upper armature and make contact of relay Z1 and ground. If the fourth digit is a No. 5, relay F will be operated, arms Di and D2 stepped to their contacts No. 4, but relay Z will remain unoperated. Consequently relay S4 will remain unoperated.

Thus it will be observed that the selecto1` arms D1 and D2 will be successively stepped by the second, third and fourth digits to contacts Nos. 2, 3 and 4, if these digits are either No. 5 or No. 0. Each No. digit will operate relays F and Z and then operate relays S2, S3 and S4 in response to the second, third or fourth No. 0 digit, respectively. If these three digits are all No. 5, none of the relays S2, S3 and S4 will be operated.

The inner upper two armatures and the lower two armatures of relay S2 are associated with eight different contacts Ki-Ks, as shown. Fig. 2 illustrates one of eight dilferent subscribers lines each of which is connected to one of the eight contacts Ki-Ks. Conductor of Fig. 2 may be connected, for example, to contact K1 of Fig. 1. The relays S2 to S4 are employed to connect a source of potential of predetermined polarity to one of the eight contacts K1 to Ka so as to apply voltage of said polarity to one of eight conductors such as conductor 5| of Fig. 2, as will now be explained.

When the code 0550 is dialed by dial D, relays S2 and S3 will be unoperated because the second and third digits of the code were 5s and not Os. Relay S4 will be operated because the fourth digit of the code dialed is a No. 0. Hence the negative potential of battery B9 will be applied to contact K1 (and to conductor 5I of Fig. 2) over a circuit which includes battery B9, resistor 35, the inner upper armature and make contact of relay S4, the inner upper armature and back contact of relay S3, the second upper armature and back contact of relay S2 to contact K1. Relay C1 of Fig. 2 operates in response to that applied potential and connects the ringing generator G1 to the local loop LPi through the two inner make contacts of relay C1. If code 0505 is dialed, relay S3 will be operated, and relays S2 and S4 will be unoperated. Positive potential is then applied to contact Ks over a circuit which includes battery Bs, resistor 29, upperarmature and back contact of relay Z, resistor 26, arm D1 and its contact No. 4, lower outer armature and back Contact of relay F, lower armature and back contact of relay S4, lower armature and make contact of relay S3, lower outer armature and back contact of relay S2 to Contact K8. The positive potential so applied will reach a relay similar to relay C1 corresponding to a different party to ring that party. So it is Iwith each of the other coded signals dialed,v the coded signals being shown adjacent to contacts K1 to Ks.

It will be observedr that contacts K1, K2, K5 and Ks receive negative potentials and that contacts K3, K4, K7 and Ks receive positive potentials. By having opposite potentials applied to contacts K1 and Ka, for example, these two contacts may be connected to a single circuit which may include oppositely poled rectiiers or polar relays or other means to separately transmit these pulses to two relays,A such as, C1 of Fig'. 2, corresponding to two different parties. Thus, one of the latter relays will be energized by positive potentials applied to the associated circuit to signal one of the parties andthe other relay will be similarly energized by negative potentials applied to the same associated circuit to signal the other ofthe parties.

After the local loop LP1, for example, receives a ringing signal, relay C1 will be released and the subscriber connected to loop LPi will be connected to line L which is in turn connected to the calling party having dial D over a switchboard circuit` of well-known type (not shown). The subscriber having loop LP1 may also be connected to other parties4 by similarA apparatus.

After the arms D1 and D2 reach their Contacts No. 4, condenser CR will receive a, substantial charge from battery Bs over a circuit which includes battery B6, resistor 2S, the lower swinger of the olf-normal switch ON and its make contact, resistor 3l, arm D2 and its Contact No, 4, resistor 38, condenser CR, resistorA 3,0l and ground. After a predetermined interval of time, such as two seconds, the charge on condenser CR will reach a value Suiicient to ionize the gas of tube VR to which it is connected by resistor 45j. Relay R will then operate over a circuit including battery Be, resistor 2Q, the lower swinger of switch ON and its contact, the winding of relay R and the anode circuit of tube VR. Relay R will cause the release magnet RL to become energized over a circuit including battery B4, the lower or operating winding of the release magnet RL, the armature of relay R and its make contact to ground. This clears all of the mechanism of selector The operation of relay R also opens the locking circuits of relaysI S2, Ss and S4 previously established bythe uppermost outer armatures and their respective make contacts, and hence these relays release if previously operated. Relay Ris employed primarily to clear out the apparatus as will be further explained hereinafter.

In the idle condition of the system condenser CR, is charged from battery B1 over a circuit which includes in addition to battery B1, the resistor Il, resistor 42, resistor 38, condenser CR, resistor 39 and ground. Resistor l2 is a very large resistor so as to restrict the charging current to a very low rate. However, condenser CR will gradually receive a potential suicient tov ionize the gas of tube VR. But relay R will not be operated because its circuit is open at the contact-I of the lower swinger of switch ON. When the rst No. 0 is dialed, the lower swinger contact will be closed to complete the circuit of relay R, but relay R will remain unoperated. This is because condenser CR will be discharged by the grounded path provided by the inner upper armature and make contact of relay F and the consequent deionization of tube VR.

During the brief intervals between the dialing of the various digits of any one of the codes, relay F will release and condenser CR will begin to receive a charge from battery B1 through the circuit of resistor 52. The intervals between digits are not large enough to allow condenser CR to reach the ionizing potential of tube VR. Relay R will then remain unoperated and the selector SE will not be cleared by its release magnet RL. Relay R and the release magnet RL will only be operated after a longer interval of time, such as four seconds, has elapsed after relay F has released. When this latter larger interval of time has. elapsed, relay R will be operated so as to clear the selector and to release any of the relays 9 S2 to S4 that may have been operated previously. After the last or fourth digit of a code has been dialed, condenser CR. will receive a charge from battery B6 over a circuit which includes the lower swinger of switch ON and its contact, resistor 37,

and relay SM is arranged to prevent the repeated operation of relay F in response to voice signals. In the `case of normal speech the first syllable may cause relays V0 and P to operate and thereby release relay SM. Condenser CF will then start to charge. But condenser CF requires a predetermined time interval, such as three-tenths of a second, to reach the ionizing voltage or" tube VF. Condenser CM will also start to charge when relay P operates. if the syllable is longer than a predetermined interval, such as fifty milliseconds, tube VM will ionize and Operate relay SM, thus discharging condenser CF. If there is a pause between syllables which is longer than the interval between two adjacent spurts oi 1,00) cycle current, tube VS will become ionized, thereby operating relay SM and discharging condenser CF. in either case relay F will not be operated and the apparatus controllingr the ringing generator will not be operated. Low level speech signals are even less likely to operate relay F because such signals are less likely to operate relays Vo and P. It is to be especially noted that false operations of the apparatus can only occur in response to four successive operations of relay F, the operations of relay F occurring within a predetermined time interval, such as four seconds, oi each other and, moreover, the :first operation of relay F must be of sufficient duration to operate relay Z or slightly less than the time required to dial a No. 0, i. e., about seven-tenths oi a second.

lt will be noted that the selector SE is of the rotary type and is illustrative of step-by-step selectors generally. It will be understood that other forms of selectors, whether of the rotary type er not, may be employed in place of selector SE within the scope of this invention.

rhe values assigned to the various constants ci the apparatus are given merely to aid in understanding the invention and are not to be construed as limitations on the apparatus.

While this invention has been shown and described in certain particular embodiments merely for illustrative purposes, it will be understood that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

l. Apparatus for selecting any one of a plurality of lines, comprising means for producing a series of A.-C. spurts approximately of a predetermined frequency and of a iirst predetermined length or a second series of A. C. spurts approximately of the same predetermined frequency` and of a second predetermined length, the different groups of spurts correspondingto different codes, a rotary switch, means responsive only to the A. C. spurts or the first predetermined length to step said switch oir normals, means responsive to 'the A. C. spurts corresponding either to the first or second predetermined lengths to further step said switch, a plurality of control elements each connected to one of the steps of the rotary switch, each control element being separately operated only in response to the C. spurts of the rst predetermined length, means including said control elements for selecting one of the lines to the exclusion of all other lines, and means to release the switch and said control elements in response to spurts other than those of the first or second predetermined lengths.

2. Apparatus for selecting any one of a plurality of lines, comprising a pulsing device for producing series of pulses, the number of pulses in each series being a variable number, a step-bystep sequence device, means for measuring the number of pulses produced by the pulsing device in each series, means controlled by said measuring means only when it responds to a plural impulse series of a given number for moving the sequence device a step from normal condition, means controlled by said measuring device for thereafter stepping the sequence device one step for each succeeding impulse series but only if said series is either of two predetermined numbers, a plurality of relays, means controlled by said sequence device for sequentially preparing said relays for operation one for each step, means controlled by said measuring means for operating the prepared relay when the corresponding impulse series corresponds in number of impulses to one of said predetermined numbers, and means controlled jointly by said relays to select one of the lines.

3. Apparatus for selectinor any one of a plurality of lines, comprising means for producing sucessive groups of pulses, said means controlling the number of pulses in any one group, a step-bystep sequence switch, means responsive to a group of pulses of predetermined number to step said switch orf normal, means for progressively stepping said switch one step at a time in response to each subsequent group of pulses if the group has more than a predetermined number of pulses, a plurality of relays one corresponding to each step of said switch, means controlled by said switch for preparing said relay for operation, one relay being prepared for operation at each step of said switch, means for operating each of said prepared relays only when the pulses of the corresponding group are of a predetermined number, and means controlled jointly by said relays to select one ot said lines.

ll. Apparatus for selecting any one of a plurality of lines, comprising means for producing successive groups or pulses, said means controlling the number of pulses in any one group, a step-bystep switch, means responsive to a group of pulses of a nrst predetermined number to step said switch 01T normal, means for progressively stepping said switch one step at a time in response to each group of pulses if the group has more than a second predetermined number of pulses, a plurality of relays, one associated with each step of said switch, means for operating each of said relays when the pulses oi' the corresponding group equals the rst predetermined number, and means controlled jointly by said relays to select one of said lines.`

5. Apparatus of selecting any one of a plurality of lines, comprising means for producing successive groups of pulses, said means controlling the number of pulses in any one group, a step-bystep switch, means responsive to a group of pulses of -a rst predetermined number to step said 'switch off normal, imeans for progressively stepping said switch one step atratme in response to each group of pulses if the group has more than a second predetermined number of pulses, a plurality of relays, one associated with each step of said switch, means for operating each of said Yrelays when the pulses of the corresponding group equal the first predetermined number, means controlled jointly by said relays to select one of said lines, and means to release said switch and said relays after said switch has been stepped a predetermined number of times.

JAMES T. NEISWINTER.

REFERENCES CITED The following references are of record in the file of this patent:

4UNITED STATES yPATENTS 

